JP2013183542A - Indirect matrix converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an indirect matrix converter which can improve the precision of current detection.SOLUTION: A converter 1 converts an input AC voltage into a DC voltage, and applies the DC voltage between a positive electrode side power supply line LH and a negative electrode side power supply line LL. A snubber circuit 2 has a capacitor C1 provided between the power supply lines LH, LL, and a diode D1 connected in series with the capacitor C1 between the power supply lines LH, LL, and including an anode on the power supply line LH side in the series path with the capacitor C1. The inverter 3 inverts the DC voltage into an AC voltage being applied to an inductive load 8. An inverter side current detection section 4 detects a current flowing through the power supply line LH or LL, between the inverter 3 and the snubber circuit 2.

Description

  The present invention relates to an indirect matrix converter, and more particularly to detection of current flowing through a DC link.

  In the indirect matrix converter, for example, a current source converter having reverse blocking and a voltage source inverter are connected to each other via a DC link. In such an indirect matrix converter, a clamp circuit is provided in the DC link in order to absorb the regenerative current from the inverter. The clamp circuit has the same configuration as a DC snubber, for example.

  Patent Document 1 is disclosed as a technique related to the present invention.

JP 2011-15604 A

  Patent Document 1 does not describe current detection. On the other hand, it has been desired to improve the accuracy of current detection.

  Thus, an object of the present invention is to provide a power conversion device that can improve the accuracy of current detection.

  According to a first aspect of the indirect matrix converter of the present invention, an AC voltage is input, the AC voltage is converted into a DC voltage, and a positive first power line (LH) and a negative second power line are converted. A converter (1) for applying the DC voltage to a power line (LL); a capacitor (C1) provided between the first and second power lines; and the first and second A snubber circuit (2) connected in series with the capacitor between power lines and having a diode (D1) including an anode on the first power line side in a series path with the capacitor; An inverter (3) that converts the voltage into an inductive load (8), and an inverter-side current detector that detects a current flowing through the first or second power line between the inverter and the snubber circuit Part (4).

  A second aspect of the indirect matrix converter according to the present invention is the indirect matrix converter according to the first aspect, provided between the first and second power supply lines (LH, LL), A second capacitor (C11) having a capacitance larger than that of the capacitor (C1), and connected in series with the second capacitor between the first and second power supply lines; A clamp circuit (5) having a second diode (D11) including an anode on the first power supply line side in a series path; and provided between the clamp circuit and the converter (1), A converter-side current detection unit (6) for detecting a current flowing through the power supply line, and one end of a series connection body of the capacitor and the diode (D1) between the clamp circuit and the inverter. Power of The other end is connected to the second power supply line on the converter side with respect to the converter-side current detection unit.

  A third aspect of the indirect matrix converter according to the present invention is the indirect matrix converter according to the second aspect, in which the converter-side current detection unit (6) is connected to the converter (5) from the clamp circuit (5). Only the current flowing through the second power supply line (LL) along the direction toward 1) is detected.

  A fourth aspect of the indirect matrix converter according to the present invention is the indirect matrix converter according to the first aspect, wherein the other end of the snubber circuit (2) is connected to the converter side current detector (6) and the inverter side. The indirect matrix converter according to claim 1, which is connected between the current detection units (4).

  A fifth aspect of the indirect matrix converter according to the present invention is the indirect matrix converter according to any one of the first to fourth aspects, wherein the snubber circuit (2) is in parallel with the capacitor (C1). A resistor (R1) connected is further provided.

  According to the first and fourth aspects of the indirect matrix converter according to the present invention, the inverter-side current detection unit detects a current flowing through the first or second power supply line between the snubber circuit and the inverter circuit. Therefore, the inverter side current detection unit does not detect the current flowing from the converter to the converter through the first electric wire, the snubber circuit, and the second power supply line. Since such a current does not flow through the inverter, only the current flowing from the inverter (3) to the inductive load (8) can be accurately compared with the case where an inverter-side current detection unit is provided between the converter and the snubber circuit. Can be detected.

  According to the second aspect of the indirect matrix converter of the present invention, the clamp circuit and the snubber circuit are output from the converter by increasing the DC voltage output from the converter due to, for example, fluctuations in the AC voltage input to the converter. A relatively large current can flow through the. Such a current flows mainly to the clamp circuit rather than the snubber circuit having a small electrostatic capacity. Since the current flowing through the clamp circuit is detected by the converter-side current detection unit, it can be detected that a large current has flowed through the converter. Therefore, the overcurrent of the converter can be detected.

  On the other hand, when a noise component caused by switching of the converter flows in the snubber circuit, the series connection body of the capacitor and the diode is connected to the second power supply line (LL) on the converter side than the capacitor side current detection unit. Therefore, the converter-side current detection unit can detect the current while avoiding this noise component. Therefore, the current flowing through the converter can be detected with high accuracy.

  On the other hand, the series connection body of the capacitor and the diode is connected to the first power supply line (LH) between the clamp circuit and the inverter. Thus, since the said series connection body is connected to the 1st power supply line by the inverter side more, the wiring inductance between an inverter and a snubber can be reduced. Thereby, for example, when a short circuit occurs in an inductive load and a current flows from the inverter to the snubber circuit, a voltage increase caused by the current and the wiring inductance can be suppressed. In addition, noise generation due to inverter switching can be reduced.

  According to the third aspect of the indirect matrix converter according to the present invention, since the regenerative current flowing from the inverter via the snubber circuit is not detected, the current flowing through the converter can be detected with higher accuracy.

  According to the fifth aspect of the indirect matrix converter of the present invention, the capacitor can be discharged via the resistor. Therefore, an increase in the voltage of the capacitor can be suppressed, and consequently, an excessive DC voltage can be suppressed from being applied to the inverter.

It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a notional structure of a power converter device. It is a figure which shows an example of a notional structure of a power converter device.

First embodiment.
As shown in FIG. 1, the indirect matrix converter includes a current source converter 1, a snubber circuit 2, a voltage source inverter 3, and an inverter-side current detection unit 4. The converter 1 inputs an AC voltage via AC lines Pr, Ps, Pt, for example. Converter 1 converts the AC voltage into a DC voltage, and applies the DC voltage between power supply lines LH and LL. Here, the potential applied to the power supply line LH is higher than the potential applied to the power supply line LL. In FIG. 1, the three-phase converter 1 connected to the three AC lines Pr, Ps, and Pt is illustrated, but the present invention is not limited to this. The converter 1 may be, for example, a single phase converter or a converter larger than three phases.

  In the example of FIG. 1, the converter 1 includes, for example, diodes Dr1, Dr2, Ds1, Ds2, Dt1, and Dt2 and switching elements Sr1, Sr2, Ss1, Ss2, St1, and St2.

  The switching elements Sx1 and Sx2 (hereinafter, x represents r, s, and t) are, for example, insulated gate bipolar transistors. Diode Dx1 and switching element Sx1 are connected in series between AC line Px and power supply line LH. The diode Dx1 is arranged with its cathode facing the power supply line LH. That is, the diodes Dr1, Ds1, and Dt1 prevent current from flowing from the power supply line LH to the AC lines Pr, Ps, and Pt via the switching elements Sr1, Ss1, and St1, respectively.

  The diode Dx2 and the switching element Sx2 are connected in series with each other between the AC line Px and the power supply line LL. The diode Dx2 is arranged with its anode facing the power supply line LL side. That is, the diodes Dr2, Ds2, and Dt2 prevent current from flowing from the AC lines Pr, Ps, and Pt to the power supply line LL via the switching elements Sr2, Ss2, and St2, respectively.

  These switching elements Sx1 and Sx2 are appropriately controlled by a control unit (not shown). For example, the switching elements Sx1 and Sx2 are controlled based on the AC voltage applied to the AC line Px. Thereby, the converter 1 can convert the alternating voltage applied to AC line Pr, Ps, Pt into a DC voltage, and can apply this between the power supply lines LH and LL. Since such control is a known technique, detailed description thereof is omitted.

  In addition, although the switching elements Sx1 and Sx2 and the diodes Dx1 and Dx2 are provided in the illustration of FIG. 1, this is not necessarily limited thereto. For example, instead of a set of the diode Dx1 and the switching element Sx2 and / or instead of a set of the diode Dx2 and the switching element Sx2, a reverse blocking type switching element (for example, RB-IGBT ( Reverse blocking insulated gate bipolar transistor) etc.) may be employed.

  The snubber circuit 2 is provided between the converter 1 and the inverter 3 and includes a diode D1 and a capacitor C1. The capacitor C1 is a ceramic capacitor, for example, and is provided between the power supply lines LH and LL. The diode D1 is connected in series with the capacitor C1 between the power supply lines LH and LL, and has an anode on the power supply line LH side. The diode D1 prevents the capacitor C1 from discharging toward the power supply line LH.

  The inverter 3 is, for example, a three-phase inverter, which converts a DC voltage between the power supply lines LH and LL into an AC voltage and applies it to the inductive load 8. The inverter 3 includes switching elements Su1, Sv1, Sw1, Su2, Sv2, Sw2, and diodes Du1, Dv1, Dw1, Du2, Dv2, Dw2, for example. The switching elements Sy1, Sy2 (y represents u, v, w) are, for example, insulated gate bipolar transistors. The switching elements Sy1 and Sy2 are connected in series between the power supply lines LH and LL. The AC line Py is drawn from a connection point connecting the switching elements Sy1 and Sy2. The diodes Dy1 and Dy2 are connected in parallel to the switching elements Sy1 and Sy2, respectively, and their anodes are provided toward the power supply line LL side.

  These switching elements Sy1, Sy2 are appropriately controlled by a control unit (not shown). By this control, the inverter 3 can convert the DC voltage between the power lines LH and LL into an AC voltage and apply it to the AC lines Pu, Pv and Pw. Since such control is a known technique, detailed description thereof is omitted.

  The inductive load 8 is a motor, for example, and is driven according to the AC voltage applied from the inverter 3.

  In the example of FIG. 1, a filter 7 is provided on the input side of the converter 1. For example, the filter 7 includes a reactor provided in each of the AC lines Pr, Ps, and Pt and a capacitor provided between the AC lines Pr, Ps, and Pt. The capacitors are provided between the reactor and the converter 1, and in the example of FIG. 1, these capacitors are connected to each other by star connection. The filter 7 suppresses the current and voltage of harmonic components due to switching of the converter 1, for example. As a result, the waveform of the input current can be smoothed. On the other hand, if the input current flowing through the AC lines Pr, Ps, and Pt is allowed to contain many harmonic components, the filter 7 is not an essential requirement.

  In this indirect matrix converter, although the capacitor C1 is provided between the power supply lines LH and LL, the capacitor C1 functions as a snubber capacitor having a small electrostatic capacity, and does not function as a smoothing capacitor. In the normal operation of the inductive load 8, the current from the converter 1 flows to the inverter 3 via the power line LH, and flows from the inverter 3 to the converter 1 via the power line LL. Therefore, in normal operation of the inductive load 8, ideally no current flows through the snubber circuit 2, and the current flowing through the converter 1 and the current flowing through the inverter 3 are equal to each other.

  On the other hand, a current flows through the snubber circuit 2 in the following cases, for example. That is, for example, when a regenerative current is generated from the inverter 3. This regenerative current is blocked by the diodes Dx1 and Dx2 and cannot flow through the converter 1, but flows through the snubber circuit from the power supply line LH to LL. Further, for example, the DC voltage output from the converter 1 may exceed the voltage across the capacitor C1 due to fluctuations in the AC voltage input to the converter 1. In such a case, a current flows from the converter 1 to the snubber circuit 2. Further, for example, a noise current caused by switching of the inverter 3 can also flow through the snubber circuit 2.

  In the present embodiment, the inverter-side current detection unit 4 detects the current flowing through the power supply line LH or the power supply line LL between the snubber circuit 2 and the inverter 3. In the illustration of FIG. 1, the inverter-side current detection unit 4 detects the current of the power supply line LL. In the illustration of FIG. 1, a shunt resistor is shown as a component belonging to the inverter-side current detection unit 4. However, it is not always necessary to use a shunt resistor, and the current may be detected by an arbitrary method.

  Since the inverter-side current detection unit 4 detects the current flowing through the power supply line LH or the power supply line LL between the snubber circuit 2 and the inverter 3, the converter 1 passes through the power supply line LH, the snubber circuit 2 and the power supply line LL. The current flowing to the converter 1 is not detected. Since this current does not pass through the inverter 3, the inverter-side current detection unit 4 is compared with the case where the inverter-side current detection unit 4 detects the current flowing through the power supply lines LH and LL between the converter 1 and the snubber circuit 2. The current flowing through the inverter 3 can be detected with high accuracy.

  The current detected by the inverter-side current detection unit 4 can be detected as line currents iu, iv, iw flowing through the AC lines Pu, Pv, Pw based on the switching pattern of the inverter 3. Since detection of such a line current is a known technique, a detailed description thereof will be omitted, but an example will be briefly described. For example, in the switching pattern in which the switching elements Su1, Sv2, and Sw2 are conducted, the line current iu flows from the power line LH through the switching element Su1 through the AC line Pu, and the current branched in the inductive load 8 is the AC lines Pv, Pw. To the power line LL via the switching elements Sv2 and Sw2. Therefore, in this switching pattern, the current flowing through the power supply line LL matches the line current iu. Therefore, the current detected by the inverter-side current detection unit 4 when this switching pattern is adopted can be detected as the line current iu. The same applies to the line currents iv and iw.

  In the present embodiment, since the current can be detected with high accuracy, the line current can be detected with high accuracy. Such a line current can be used to control the inverter. Therefore, the current (iu, iv, iw) flowing through the inductive load 8 is detected with high accuracy, thereby contributing to appropriate inverter control.

Second embodiment.
The indirect matrix converter shown in FIG. 2 includes a clamp circuit 5 and a converter-side current detection unit 6 as compared with the indirect matrix converter shown in FIG. The clamp circuit 5 includes a diode D11 and a capacitor C11. The capacitor C11 is provided between the power supply lines LH and LL, and has a larger capacitance than the capacitance of the capacitor C1. Further, the impedance of the capacitor C11 in the harmonic region is larger than the impedance of the capacitor C1 in the harmonic. The capacitor C11 is, for example, an electrolytic capacitor, and the capacitor C1 is, for example, a film capacitor. The diode D11 is connected in series with the capacitor C11 between the power supply lines LH and LL, and has an anode on the power supply line LH side in the series path with the capacitor C11. The diode D11 prevents the capacitor C11 from discharging to the power supply line LH side.

  Converter-side current detection unit 6 detects a current flowing through power supply line LL between converter 1 and clamp circuit 5. In the illustration of FIG. 2, a shunt resistor is shown as a component belonging to the converter-side current detection unit 6. However, it is not always necessary to use a shunt resistor, and the current may be detected by an arbitrary method.

  One end of the series connection body of the diode D1 and the capacitor C1 belonging to the snubber circuit 2 is connected to the power supply line LH between the clamp circuit 5 and the inverter 3. According to this, the wiring inductance between the one end and the inverter 3 can be reduced as compared with the structure in which the one end is connected to the power supply line LH on the converter 1 side of the clamp circuit 5.

  The rate of increase (di / dt) with respect to time is the highest in both power running and regenerative current when at least any two of the AC lines Pu, Pv, Pw are short-circuited. At this time, the voltage rise (L · di / dt) due to the regenerative current and the wiring inductance becomes the highest. In the second embodiment, the wiring inductance is reduced as described above, and the snubber circuit 2 can absorb an instantaneous overcurrent more than the clamp circuit 5, so that this voltage rise is suppressed. Can do.

  On the other hand, the other end of the series connection body of the diode D1 and the capacitor C1 is connected to the power supply line LL on the converter 1 side with respect to the converter-side current detection unit 6. In other words, converter-side current detection unit 6 detects a current flowing through power supply line LL between snubber circuit 2 and clamp circuit 5. Therefore, converter-side current detection unit 6 does not detect the current flowing through power supply line LL to the converter 1 side via snubber circuit 2.

  Since the regenerative current flows through the snubber circuit 2, the converter side current detector 6 can detect the regenerative current. However, ideally, no current flows through the converter 1 when a regenerative current flows. This is because the voltage across the capacitors C1 and C11 is higher than the maximum value of the AC voltage (line voltage) input to the converter 1. Therefore, it can be determined that the current flowing through the converter is zero as the converter-side current detection unit 6 detects the regenerative current.

  Converter-side current detector 6 may detect only the current flowing through power supply line LL along the direction from clamp circuit 5 to converter 1. As a result, no regenerative current is detected as the current flowing through the converter 1.

  Similar to the first embodiment, for example, due to fluctuations in the AC voltage input to the converter 1, the converter 1 relatively passes through the power supply line LH, the clamp circuit 5, the snubber circuit 2, and the power supply line LL. A large current can flow. However, the capacitance of the capacitor C11 belonging to the clamp circuit 5 is larger than the capacitance belonging to the snubber circuit 2, for example, 10 times or more. Therefore, such a current mainly passes through the clamp circuit 5. Therefore, the converter-side current detection unit 6 can detect the current flowing through the clamp circuit 5 without detecting the current flowing through the snubber circuit 2. Therefore, it can be detected that a large current has occurred in converter 1.

  On the other hand, the impedance in the harmonic component of the capacitor C1 is smaller than the impedance in the harmonic component of the capacitor C11. In addition, the impedance in a harmonic component here is an impedance in a harmonic component higher than the minimum value of the switching frequency of the inverter 3, for example. Alternatively, for example, when the switching signal to the inverter 3 is generated by comparing a predetermined carrier with a command value, the impedance may be in a higher harmonic component than the frequency of the carrier.

  As described above, since the impedance of the harmonic component of the capacitor C1 is smaller than the impedance of the harmonic component of the capacitor C11, harmonic components such as noise caused by switching of the inverter 3 (hereinafter referred to as noise current) are generated by the clamp circuit 5. Rather than the snubber circuit 2. More specifically, due to switching of the inverter 3, a current corresponding to the inductance component of the power supply line LH between the filter 7 and the inverter 3 flows through the snubber circuit 2 as switching noise. Therefore, noise current may flow from the filter 7, the converter 1 and the power supply line LH to the power supply line LL, the converter 1 and the filter 7 through the snubber circuit 2, or from the inverter 3 and the power supply line LH through the snubber circuit 2. In some cases, a noise current flows to the power supply line LL and the inverter 3.

  A converter 1 and a clamp circuit 3 are provided between the filter 7 and the snubber circuit 2 on the power supply line LH side. Therefore, the inductance component between the filter 7 and the snubber circuit 2 is larger than the inductance component between the snubber circuit 2 and the inverter 3. Therefore, the noise current flowing into the snubber circuit 2 from the clamp circuit 5 side is larger than the noise current flowing into the snubber circuit 2 from the inverter 3 side.

  In the second embodiment, the snubber circuit 2 is connected to the DC line LL between the converter 3 and the converter-side current detection unit 6. Therefore, the noise current flowing into the snubber circuit 2 from the inverter 3 side flows through the converter side current detection unit 6, but the noise current flowing into the snubber circuit 2 from the clamp circuit 5 side does not flow through the converter side current detection unit 6. As described above, since the noise current is relatively small from the inverter 3 side, the converter-side current detection unit 6 can detect the current flowing through the converter 1 with relatively high accuracy.

<Snubber circuit>
In the illustration of FIG. 3, the snubber circuit 2 further includes a resistor R1. The resistor R1 is connected in parallel with the capacitor C1. Therefore, the capacitor C1 can be discharged via the resistor R1. Therefore, an increase in the voltage of the capacitor C1 can be suppressed, and the absorption capacity of the high frequency current is improved.

  On the other hand, if the capacitor C1 is discharged and the voltage of the capacitor C1 becomes smaller than the DC voltage output from the converter 1, a current flows from the converter 1 through the power supply line LH to the snubber circuit 2. For example, if the converter 1 applies a DC voltage between the power supply lines LH and LL as follows, this current tends to flow periodically. That is, converter 1 alternately switches the largest maximum phase line voltage and the next largest intermediate phase line voltage among the input line voltages, and outputs the result as a DC voltage. Therefore, when the DC voltage is switched from the intermediate phase line voltage to the maximum phase line voltage, the DC voltage increases relatively steeply. Therefore, the DC voltage tends to exceed the voltage of the capacitor C1 at the time of switching, and thus this current easily flows. However, even if such a current flows through the snubber circuit 2, the current is not detected by the inverter-side current detection unit 4 and the converter-side current detection unit 6. Therefore, the inverter-side current detection unit 4 can detect the current flowing through the inverter 3 with high accuracy. This content is also applied to the case where the snubber circuit 2 has the resistor R1 in the first embodiment.

<Clamp circuit>
The clamp circuit 5 illustrated in FIG. 3 further includes a capacitor C12 and diodes D12 and D13 as compared with the clamp circuit 5 of FIG. Diode D11 and capacitors C11 and C12 are connected in series between power supply lines LH and LL. In the series path, the diode D11 has an anode on the power supply line LH side, and is provided between the capacitors C11 and C12. In the series path, the capacitor C11 is provided on the power supply line LH side with respect to the diode D11. The diode D12 is provided between the connection point between the capacitor C11 and the diode D11 and the power supply line LL. The diode D12 has an anode on the power supply line LL side. The diode D13 is provided between the connection point between the capacitor C12 and the diode D11 and the power supply line LH. The diode D13 has a cathode on the power supply line LH side.

  3 further includes switch elements S11 and S12, a resistor R11, and a diode D14. The switch element S11 is connected in parallel with the diode D11. The resistor R11 is connected in series with the diode D11 between the capacitors C11 and C12 in the series path of the capacitors C11 and C12 and the diode D11. A series body of the diode D11 and the resistor R11 is sandwiched between the diodes D12 and D13. The switch element S12 is an insulated gate bipolar transistor, for example, and is connected in parallel with the resistor R11.

  When the switch elements S11 and S12 are rendered non-conductive by the clamp circuit 5, the capacitors C11 and C12 are charged while being connected in series with each other, and discharged while being connected in parallel with each other. According to the clamp circuit 5, as described in Patent Document 1, for example, the capacitors C <b> 11 and C <b> 12 can charge and discharge according to the load power factor of the inductive load 8. However, even in the clamp circuit 5 of FIG. 3, the DC voltage increases if the load power factor decreases. Therefore, also in the clamp circuit 5 of FIG. 3, if the switch elements S11 and S12 are turned on when the regenerative current is larger than the predetermined value Iref1, the capacitors C11 and C12 can be discharged when the powering current flows. Therefore, an increase in DC voltage can be suppressed.

  Since the resistor R11 exists in the charging path of the capacitors C11 and C12, that is, the series path, for example, the inrush current flowing through the capacitors C11 and C12 can be reduced when charging the capacitors C11 and C12. In addition, when the AC voltage applied to the AC lines Pr, Ps, Pt drops instantaneously and the AC voltage is recovered thereafter, an inrush current can flow to the capacitors C11, C12. The current can also be reduced. On the other hand, when a regenerative current flows to the capacitors C11 and C12, the DC voltage between the power lines LH and LL increases by the voltage drop at the resistor R1. Therefore, the switch element S12 may be turned on when the regenerative current is larger than the predetermined value Iref1. Thereby, since the regenerative current flows avoiding the resistor R11, an increase in the DC voltage due to the voltage drop of the resistor R11 can be avoided. Moreover, since no current flows through the resistor R11 by short-circuiting the resistor R11, heat generation of the resistor R11 can be suppressed, and the power capacity of the resistor R11 can be minimized.

  The diode D14 has an anode on the power supply line LL side in the charging path of the capacitors C11 and C12. This is because it is assumed that the switch element S12 does not flow current in the forward direction of the diode D14. That is, in order for the capacitors C11 and C12 to function as smoothing capacitors, it is necessary to charge and discharge the capacitors C11 and C12 in both directions. However, in the illustration of FIG. 3, since the switch element S12 conducts only in one direction, the diode D14 can conduct in the opposite direction. Therefore, for example, if the switch element S12 is a bidirectional switch, the diode D14 is unnecessary.

  In the normal operation of the inductive load 8, the switch element S12 is preferably made non-conductive. This is due to the following reason. That is, as described in Patent Document 1, for example, the DC voltage from the converter 1 may exceed the voltage across a pair of capacitors C11 and C12 as the AC voltage on the AC lines Pr, Ps, and Pt varies. In this case, a large current flows through the capacitors C11 and C12, and there is a possibility that the overcurrent is stopped. However, the resistor R11 can reduce such a current.

  As illustrated in FIG. 4, the snubber circuit 2 may be connected to the power supply line LL between the inverter current detection circuit 4 and the converter current detection circuit 6. Even in this case, as in the first embodiment, the current flowing from the converter 3 to the snubber circuit 2 does not flow through the inverter-side current detection unit 4. Therefore, the same effect as that of the first embodiment can be brought about. Moreover, the regenerative current from the inverter 3 flows avoiding the converter-side current detection circuit 6. Therefore, for example, heat generation of the shunt resistor of the converter-side current detection unit 6 due to the regenerative current can be suppressed. Further, the increase of the DC voltage when the regenerative current flows can be suppressed by the amount of the shunt resistance and the amount of the inductance component between the inverter-side current detection unit 4 and the converter-side current detection unit 6.

DESCRIPTION OF SYMBOLS 1 Converter 2 Snubber circuit 3 Inverter 4 Inverter side current detection part 5 Clamp circuit 6 Converter side current detection part C1, C11 Capacitor D1, D11 Diode LH, LL Power supply line R1 Resistance

Therefore, an object of the present invention is to provide an indirect matrix converter that can improve the accuracy of current detection.

According to a first aspect of the indirect matrix converter of the present invention, an AC voltage is input, the AC voltage is converted into a DC voltage, and a positive first power line (LH) and a negative second power line are converted. A converter (1) for applying the DC voltage to a power line (LL); a capacitor (C1) provided between the first and second power lines; and the first and second A snubber circuit (2) connected in series with the capacitor between power lines and having a diode (D1) including an anode on the first power line side in a series path with the capacitor; An inverter (3) that converts the voltage into an inductive load (8), and an inverter-side current detector that detects a current flowing through the first or second power line between the inverter and the snubber circuit part (4), said first and said second power supply lines (LH, LL) A second capacitor (C11) having a capacitance larger than that of the capacitor (C1), and connected in series with the second capacitor between the first and second power supply lines, A clamp circuit (5) having a second diode (D11) including an anode on the first power line side in a series path with two capacitors, and provided between the clamp circuit and the converter (1); A converter-side current detector (6) for detecting a current flowing through the second power supply line, and one end of a series connection body of the capacitor and the diode (D1) is provided between the clamp circuit and the inverter. The other end is connected to the second power supply line on the converter side with respect to the converter-side current detection unit .

A second aspect of the indirect matrix converter according to the present invention is the indirect matrix converter according to the first aspect, wherein the converter-side current detection unit (6) is connected to the converter ( Only the current flowing through the second power supply line (LL) along the direction toward 1) is detected.

A third aspect of the indirect matrix converter according to the present invention is the indirect matrix converter according to the first or second aspect, wherein the snubber circuit (2) is a resistor connected in parallel to the capacitor (C1). (R1) is further provided.

According to the first aspect of the indirect matrix converter of the present invention, the inverter-side current detection unit detects a current flowing through the first or second power supply line between the snubber circuit and the inverter circuit. Therefore, the inverter side current detection unit does not detect the current flowing from the converter to the converter through the first electric wire, the snubber circuit, and the second power supply line. Since such a current does not flow through the inverter, only the current flowing from the inverter (3) to the inductive load (8) can be accurately compared with the case where an inverter-side current detection unit is provided between the converter and the snubber circuit. Can be detected.

In addition , a relatively large current can flow from the converter to the clamp circuit and the snubber circuit due to an increase in the DC voltage output from the converter due to, for example, fluctuations in the AC voltage input to the converter. Such a current flows mainly to the clamp circuit rather than the snubber circuit having a small electrostatic capacity. Since the current flowing through the clamp circuit is detected by the converter-side current detection unit, it can be detected that a large current has flowed through the converter. Therefore, the overcurrent of the converter can be detected.

According to the second aspect of the indirect matrix converter according to the present invention, since the regenerative current flowing from the inverter via the snubber circuit is not detected, the current flowing through the converter can be detected with higher accuracy.

According to the third aspect of the indirect matrix converter of the present invention, the capacitor can be discharged through the resistor. Therefore, an increase in the voltage of the capacitor can be suppressed, and consequently, an excessive DC voltage can be suppressed from being applied to the inverter.

On the other hand, a current flows through the snubber circuit 2 in the following cases, for example. That is, for example, when a regenerative current is generated from the inverter 3. This regenerative current is blocked by the diodes Dx1 and Dx2 and cannot flow through the converter 1, but flows through the snubber circuit 2 from the power supply line LH to LL. Further, for example, the DC voltage output from the converter 1 may exceed the voltage across the capacitor C1 due to fluctuations in the AC voltage input to the converter 1. In such a case, a current flows from the converter 1 to the snubber circuit 2. Further, for example, a noise current caused by switching of the inverter 3 can also flow through the snubber circuit 2.

Second embodiment.
The indirect matrix converter shown in FIG. 2 includes a clamp circuit 5 and a converter-side current detection unit 6 as compared with the indirect matrix converter shown in FIG. The clamp circuit 5 includes a diode D11 and a capacitor C11. The capacitor C11 is provided between the power supply lines LH and LL, and has a larger capacitance than the capacitance of the capacitor C1. Further, the impedance of the capacitor C11 in the harmonic region is larger than the impedance of the capacitor C1 in the harmonic region . The capacitor C11 is, for example, an electrolytic capacitor, and the capacitor C1 is, for example, a film capacitor. The diode D11 is connected in series with the capacitor C11 between the power supply lines LH and LL, and has an anode on the power supply line LH side in the series path with the capacitor C11. The diode D11 prevents the capacitor C11 from discharging to the power supply line LH side.

A converter 1 and a clamp circuit 5 are provided between the filter 7 and the snubber circuit 2 on the power supply line LH side. Therefore, the inductance component between the filter 7 and the snubber circuit 2 is larger than the inductance component between the snubber circuit 2 and the inverter 3. Therefore, the noise current flowing into the snubber circuit 2 from the clamp circuit 5 side is larger than the noise current flowing into the snubber circuit 2 from the inverter 3 side.

In the second embodiment, the snubber circuit 2 is connected to the DC line LL between the converter 1 and the converter-side current detection unit 6. Therefore, the noise current flowing into the snubber circuit 2 from the inverter 3 side flows through the converter side current detection unit 6, but the noise current flowing into the snubber circuit 2 from the clamp circuit 5 side does not flow through the converter side current detection unit 6. As described above, since the noise current is relatively small from the inverter 3 side, the converter-side current detection unit 6 can detect the current flowing through the converter 1 with relatively high accuracy.

<Clamp circuit>
The clamp circuit 5 illustrated in FIG. 3 further includes a capacitor C12 and diodes D12 and D13 as compared with the clamp circuit 5 of FIG. Diode D11 and capacitors C11 and C12 are connected in series between power supply lines LH and LL. In the series path, the diode D11 has an anode on the power supply line LH side, and is provided between the capacitors C11 and C12. In the series path, the capacitor C11 is provided on the power supply line LH side with respect to the diode D11. Diode D 13 is provided between a connection point between the capacitor C11 and the diode D11, a power supply line LL. Diode D 13 has an anode power supply line LL side. Diode D 12 is provided between the connection point between the capacitor C12 and the diode D11, a power supply line LH. Diode D 12 has a cathode to the power supply line LH side.

As illustrated in FIG. 4, the snubber circuit 2 may be connected to the power supply line LL between the inverter- side current detection circuit 4 and the converter- side current detection circuit 6. Even in this case, the current flowing from the converter 1 to the snubber circuit 2 does not flow through the inverter-side current detection unit 4 as in the first embodiment. Therefore, the same effect as that of the first embodiment can be brought about. Moreover, the regenerative current from the inverter 3 flows avoiding the converter-side current detection circuit 6. Therefore, for example, heat generation of the shunt resistor of the converter-side current detection circuit 6 due to the regenerative current can be suppressed. Further, it is possible to suppress an increase in the shunt resistance of minutes, only a minute inductance component between the inverter-side current detection unit 4 and the converter-side current detection unit 6, the DC voltage when the regenerative current flows.

Claims (5)

An AC voltage is input, the AC voltage is converted into a DC voltage, and the DC voltage is applied between the positive first power line (LH) and the negative second power line (LL). Converter (1),
A capacitor (C1) provided between the first and second power supply lines and a capacitor connected in series between the first and second power supply lines, and in a series path with the capacitor A snubber circuit (2) having a diode (D1) including an anode on the first power line side;
An inverter (3) for converting the DC voltage into an AC voltage and applying it to the inductive load (8);
An indirect matrix converter comprising: an inverter-side current detection unit (4) that detects a current flowing through the first or second power line between the inverter and the snubber circuit. A second capacitor (C11) provided between the first and second power supply lines (LH, LL) and having a larger capacitance than the capacitor (C1); and the first and second A clamp circuit (5) connected in series with the second capacitor between the power supply lines and having a second diode (D11) including an anode on the first power supply line side in a series path with the second capacitor; ,
A converter-side current detector (6) provided between the clamp circuit and the converter (1) and detecting a current flowing through the second power line;
One end of a series connection body of the capacitor and the diode (D1) is connected to the first power line between the clamp circuit and the inverter, and the other end is on the converter side than the converter-side current detection unit. The indirect matrix converter according to claim 1, wherein the indirect matrix converter is connected to the second power line.   The converter-side current detection unit (6) detects only a current flowing through the second power supply line (LL) along a direction from the clamp circuit (5) toward the converter (1). The indirect matrix converter described.   The indirect matrix converter according to claim 1, wherein the other end of the snubber circuit (2) is connected between the converter-side current detection unit (6) and the inverter-side current detection unit (4).   The indirect matrix converter according to any one of claims 1 to 4, wherein the snubber circuit (2) further includes a resistor (R1) connected in parallel to the capacitor (C1).

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